Reduction of radiation-related anxiety promoted wellbeing after the 2011 disaster: 'Fukushima Health Management Survey'.

After the Fukushima disaster in 2011, affected residents experienced increased radiation-related anxiety and reduced subjective wellbeing. We investigated whether reduction of radiation-related anxiety promoted wellbeing among evacuees in Fukushima and assessed the role of mental health distress as a mediator. We used data from questionnaire surveys of evacuees in the 2011 and 2012 fiscal years (N = 34 312). We used radiation risk perception as an indicator of radiation-related anxiety and the frequency of laughter as an indicator of wellbeing. We measured changes in radiation risk perception from 2011 and 2012, and the frequencies of laughter and mental health distress (Kessler 6-item scale) in 2012, and investigated associations between radiation risk perception and frequency of laughter with and without covariates of mental health distress. Perceived genetic risk in 2011 had a significant inverse association with the frequency of laughter. Lowering of radiation risk perception was significantly associated with the frequency of laughter in the absence of covariates of mental health distress, but not in their presence. Lowering of radiation risk perception was also significantly associated with low mental health distress. Reduction of radiation-related anxiety promoted wellbeing via alleviation of mental health distress.